Polyphenylene ethers are a widely-used class of thermoplastic engineering resins characterized by excellent hydrolytic stability, dimensional stability, toughness, heat resistance and dielectric properties. They are also resistant to high temperature conditions under many circumstances.
A disadvantage of polyphenylene ethers which militates against their use in certain applications and particularly certain automotive applications is their low resistance to non-polar solvents such as gasoline. In several copending applications which will be described in greater detail below, highly compatible polymer blends of polyphenylene ether and linear polyester resins provide beneficial improvements in the chemical resistance required for automotive applications. Such automotive applications include molded thermoplastic body panels.
However, chemical resistance is not the only important physical property of such thermoplastic blends. In particular, for certain automotive applications, it is desirable that the molded thermoplastic product exhibit improved impact strength. As will be seen in the examples below, this goal is accomplished without unreasonably sacrificing other physical properties of the thermoplastic resin.
In co-pending commonly-owned application, Ser. No. 891,457 filed July 29, 1986, there are disclosed highly compatible polymer blends having a high degree of impact resistance and solvent resistance. These blends comprise at least one polyphenylene ether or blend thereof with at least one polystyrene, at least one poly(alkylene dicarboxylate), at least one elastomeric polyphenylene ether-compatible impact modifier, and at least one polymer containing a substantial proportion of aromatic polycarbonate units. Illustrative of the linear polyesters are the poly(alkylene dicarboxylates) and especially the poly(alkylene terephthalates). In copending, commonly owned application, Ser. No. 010,867 filed Feb. 4, 1987, there are disclosed similar polymer blends which are highly compatible and have high solvent resistance and favorable tensile properties but which are particularly useful in applications where impact strength is not the primary consideration.
Filled versions of compatible polyphenylene ether-polyester blends having good surface appearance and coefficients of thermal expansion can be seen in co-pending commonly owned applications Ser. No. 085,034, Filed Aug. 12, 1987 and Ser. No. 031,344, Filed Mar. 26, 1987. A glass and phosphorous compound blend of PPE and polyester may be seen in U.S. Pat. No. 4,672,086 (Seilers, et al.).
The use of olefin-acrylate copolymers as modifiers in polyphenylene ether-polyamide systems may be seen in copending application Ser. No. 122,954, Filed Mar. 26, 1987.
The improvements in impact strength found in compositions of the present invention are accomplished by incorporation of effective property improving amounts of alkylene acrylate copolymers, including functionalized versions thereof, in the polyphenylene ether - linear polyester base resin composition.